\documentstyle[latexsym,12pt]{article}     % in LaTeX2.09
% or alternatively in LaTeX2e the following two lines:
%\documentclass[12pt]{article}            % in LaTeX2e instead of \documentstyle
%\usepackage{latexsym}                    % in LaTeX2e instead of \documentstyle
  \textwidth 140mm             % <-- preamble, declarations etc. may be placed here
                               %               (no text may be produced here!)
\begin{document}
  The text starts here.        % <-- text production
\end{document}
